Multi-Scale Modeling of Texture Evolution in Beryllium and Zirconium during Equal Channel Angular Extrusion

Irene J Beyerlein,G.G Yapici,Carlos N Tomé,Ibrahim Karaman,Laurent Capolungo

doi:10.4028/www.scientific.net/msf.633-634.483

Irene J Beyerlein, G.G Yapici + Show 3 more

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https://doi.org/10.4028/www.scientific.net/msf.633-634.483

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Abstract

This work studies the deformation mechanisms active in two pure hexagonal close packed metals, beryllium (Be) and zirconium (Zr), during equal channel angular extrusion processing. An experimental-theoretical approach is employed to assess their relative contributions through measurement and calculation of texture evolution. A new multi-scale constitutive model, incorporating thermally activated dislocation density based hardening, is shown to effectively predict texture evolution as a function of processing route, number of passes (up to four), initial texture, pressing rate, and processing temperature. Texture predictions are shown to be in very good agreement with experimental measurements. Also, it is found that the two most active deformation modes in Be are basal slip and prismatic slip, where the predominant one is interestingly found to depend on die angle. Deformation in Zr during the first pass is predicted to be accommodated not only by its easiest mode, prismatic slip, but by basal slip and tensile twinning.

Highlights

There is a growing interest in fabricating ultra-fine grained metals with a hexagonal close packed crystal structure via severe plastic deformation (SPD) techniques in order to improve their mechanical properties (e.g yield strength)
Texture evolution depends on processing route
Texture evolution can only be adequately modeled with basal slip; not shown here, suppressing basal slip leads to grossly inaccurate predictions

Summary

Introduction

There is a growing interest in fabricating ultra-fine grained metals with a hexagonal close packed (hcp) crystal structure via severe plastic deformation (SPD) techniques in order to improve their mechanical properties (e.g yield strength) One such technique, equal channel angular extrusion (ECAE) [1], referred to as equal channel angular pressing (ECAP), has been applied to Ti [25], Mg [6,7,8,9,10,11,12], Be [13,14,15], and Zr [16,17,18,19,20,21]. In this work we study texture evolution in pure Be and Zr during ECAE using a multi-scale constitutive model These two hcp metals and their alloys are used in nuclear applications, where knowledge of their structural performance is needed. The relative contribution of each has been shown to depend on crystal orientation, temperature, and strain rate

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